1. Field of the Invention
The present invention relates, generally, to an injection molding system having a degating device used in the manufacture of molded articles and, more specifically, to an injection molding system having a removable, in-mold, degating device for severing the molded article from flash material.
2. Description of the Related Art
Plastic injection molding is a conventionally known manufacturing process. The process typically involves the transfer of molten thermoplastic material from an injection cylinder through a runner system, including a sprue, through a gate, and ultimately into a mold cavity formed by a die. The die is typically separated into halves. One or both of the halves may include at least one opening to permit conveyance of the molten thermoplastic material into the mold cavity. The mold cavity corresponds to the shape of the article to be molded. The point at which the runner system communicates with the opening to the mold cavity is commonly referred to as a gate. A gate is typically either a fixed member that is integrated into the mold assembly or attached to the end of the molten thermoplastic injection machine. Gates generally have a tapered internal conduit through which the molten thermoplastic material enters the mold cavity at a rate determined by the size of the gate outlet.
After the thermoplastic material fills the mold cavity and solidifies, the article may be removed from the mold cavity. However, the injection molding process produces excess thermoplastic material that solidifies within the gate and a portion of the runner system that remains attached to the molded article. This excess material is commonly known in the art as “flash.” The act of removing flash is known as degating.
Current technology within the field includes the use of degating machines that shear off the flash after the article is removed from the mold or involve removing the molded article in a manner perpendicular to that of the gate to effectively utilize an edge of the gate to remove the flash from the molded article. Incorporation of a degating machine into the injection molding manufacturing process is a costly venture. In some cases, the incremental cost associated with degating machines often prohibits their use in order to maintain a competitive price for the manufactured article.
In response to this problem, gating devices were developed in the related art that include edges used to degate the molded article. The following United States patents disclose the use of the edge of a gate as a degating device.
U.S. Pat. No. 3,371,385, issued to A. Cordio et al., discloses an injection mold assembly with a shearing means in connection with creating soles for shoes. The Cordio et al. device utilizes a small cylindrical gate to inject molten material into a shoe sole mold and the edge of the gate to sever the flash upon removal of the shoe sole from the mold. However, the severed flash that remains within the gate and runner within the mold must be removed after each molding event.
U.S. Pat. No. 3,737,271, issued to George J. Novak, discloses an apparatus having a gate with a sharpened, knife-like edge for severing excess material from the molded product. However, the degating device disclosed by Novak forms a permanent part of the die that defines the mold.
While gating devices that employ a degating edge are known to alleviate some of the problems associated with removing flash material from a molded article, they are generally limited for use in connection with the die in which they are integrated. In other words, the gating devices are integrally formed or associated with a particular die and therefore may not be removed or used with other dies as the need arises. Likewise, the die is limited to the particular gate and its restrictions, which includes, for example, the size of the gate outlet. Moreover, the devices disclosed in the aforementioned patents do not alleviate the problem of removing the flash from the runner system, namely from within the gate and runner within the mold.
Accordingly, while the gating devices having degating edges of the type known in the related art and the molding assemblies incorporating these devices have generally worked for their intended purposes, there exists a need in the art for a simple, cost effective gating device that incorporates a degating edge that is removably mounted to the molding assembly and that also facilitates ejecting the flash within the gate and runner system at the conclusion of each molding event.